Hateful, detestable, offensive, revolting, arousing strong dislike or aversion.
→ The English language has a plethora of words that mean hateful or offensive, so odious has many synonyms. Here is a selection of them, ranging from the familiar to the not-so-familiar: disgusting, obnoxious, objectionable, disagreeable, contemptible, repellent, repugnant (ri-PUHG-nint), loathsome (LOHTH-sum), abominable, abhorrent (ab-HOR-int), heinous (HAY-nis), opprobrious (uh-PROHbree-us), flagitious (fluh-JISH-us, word 46 of Level 9), and last but not least, the thoroughly damning word execrable (EK-si-kruhbuul). By derivation execrable means expressing a curse, and today the word applies to that which is so horrible or wicked that it deserves to be cursed or damned.
Odious comes from the Latin odiosus, hateful, which in turn comes from odium, hatred, the direct source of the English noun odium (OH-dee-um). Odium and hatred are synonymous, but odium refers less frequently to hatred directed toward someone or something else and more often to hatred experienced or incurred: “Alan’s supervisor was a supercilious, draconian tyrant who did not seem to care that her employees regarded her with odium.”
The adjective odious refers either to that which arouses hate, disgust, or displeasure or to that which is regarded as hateful, detestable, or offensive. An odious remark is extremely unpleasant or offensive; an odious practice is a disagreeable or disgusting practice; an odious person is a person that others find hateful or detestable.
The corresponding noun odiousness means the state or quality of being odious, as the odiousness of the crime.
Be careful to distinguish odious from odorous both in spelling and usage. Odorous means emitting an odor, having a distinct aroma or smell. Odious means hateful, detestable, revolting. Odorous armpits or odorous garbage may be odious, but there is nothing odious, hateful or offensive, about odorous flowers.